CAPTURE_RING_BUFFER_SIZE
kmalloc(CAPTURE_RING_BUFFER_SIZE, GFP_KERNEL);
(CAPTURE_RING_BUFFER_SIZE -
CAPTURE_RING_BUFFER_SIZE - read_ptr;
CAPTURE_RING_BUFFER_SIZE;
size_t bytes_to_end = CAPTURE_RING_BUFFER_SIZE - write_ptr;
CAPTURE_RING_BUFFER_SIZE;